When grains are processed into flour or cereals, the primary concern is loss of nutrients. However, if you grind your own grains or use products that are made from the whole grain without discarding anything, you get all or most of the nutrients of the original grain. But grains that have been broken apart in any way will be digested more quickly. That’s a big disadvantage for diabetics and dieters.
Carbohydrates are long chains of sugars, and only single sugars can be absorbed from your intestines into your bloodstream. The foods that cause rapid rise in blood sugar are those that are digested most quickly; the worst offenders are sugar and anything made from flour. When you eat whole grains (seeds), it takes a long time to break apart the capsule, separate the carbohydrates from the fiber, and completely digest each grain. Your blood sugar rises slowly, stays slightly elevated for a long time (so you don’t feel hungry again soon after eating) and never reaches the high levels that come from sugar or flour.
Don’t be misled by popular authors who tell you gluten is the culprit; flours made from rice, corn and other gluten-free sources cause the same high rise in blood sugar as flour made from wheat.
Grains that are eaten as whole seeds are also more filling and satisfying because they have more bulk and take longer to break down. Part of their bulk comes from water: each seed swells up when it cooks and soaks up water, which is carried in the grain until it is completely broken down in your digestive tract. (The water you drink, on the other hand, is absorbed directly from your stomach almost as soon as it gets there. Water and other liquids do not “fill you up.”) Processed grains absorb some water when you cook them, but less than the whole seeds; and the water is separated out more quickly during the digestive process. Most people can easily eat two or three cups of pasta, but you will find that you feel full with just a cup of whole grains, or even less.
The whole grains are chewy and take more time to eat. Some of the seeds are broken apart by your chewing, but not all of them. Some of the grains may even pass through your system undigested. On the other hand, anything made from flour or grains that have been cut, flaked, rolled or shredded has been thoroughly pre-chewed and pre-digested for you. You may get all the nutrients of the whole grains, but you don’t get the full benefits of bulk and slow transit through your digestive system.
Whole grain pastas, breads and cereals provide more nutrients than refined grain products, but to get ALL of the benefits of whole grains, eat the seeds themselves. See Why Whole Grains are Healthful